U.S. patent number 6,011,980 [Application Number 08/900,703] was granted by the patent office on 2000-01-04 for wireless telecommunication equipment.
This patent grant is currently assigned to Oki Electric Industry Co., Ltd.. Invention is credited to Tsutomu Katsuyama, Tomonori Nagano, Waho O.
United States Patent |
6,011,980 |
Nagano , et al. |
January 4, 2000 |
Wireless telecommunication equipment
Abstract
A wireless telecommunication equipment having a receiver portion
and a transmitter portion. An automatic gain control amplifier
having a gain varied in accordance with an automatic gain control
signal input thereto is located in the receiver portion of the
equipment, and a transmission power control amplifier having a gain
varied in accordance with an open loop control signal input thereto
is located in the transmitter portion of said equipment. The
automatic gain control and the transmission power control
amplifiers have the same operating characteristics.
Inventors: |
Nagano; Tomonori (Tokyo,
JP), O; Waho (Tokyo, JP), Katsuyama;
Tsutomu (Tokyo, JP) |
Assignee: |
Oki Electric Industry Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
16740999 |
Appl.
No.: |
08/900,703 |
Filed: |
July 25, 1997 |
Foreign Application Priority Data
|
|
|
|
|
Aug 21, 1996 [JP] |
|
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8-219786 |
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Current U.S.
Class: |
455/572; 330/279;
455/126; 455/69; 455/245.1 |
Current CPC
Class: |
H03G
3/3042 (20130101); H04W 52/52 (20130101); H04W
52/10 (20130101); H03G 3/3078 (20130101) |
Current International
Class: |
H03G
3/20 (20060101); H04B 7/005 (20060101); H03G
3/30 (20060101); H04B 007/00 () |
Field of
Search: |
;455/69,234.1,234.2,239.1,240.1,245.1,245.2,522 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
TIA/EIA/Interim Standard-95-A, Mobile Station-Base Station
Compatibility Standard for Dual-Mode Wideband Spread Spectrum
Cellular System, pp. 6-1/6-10, May 1995. .
Hefeng Wang et al., "CD3000B Portable Telephone for CDMA Cellular
Systems", OKI Technical Review 156, pp. 71-74 Jul. 1996. .
TIA/EIA/IS-95-A, pp. 6-6..
|
Primary Examiner: Chin; Wellington
Assistant Examiner: Tran; Pablo N.
Attorney, Agent or Firm: Venable Frank; Robert J.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of Japanese Application Serial
No. 219786/1996 filed Aug. 21, 1996, the subject matter of which is
incorporated herein by reference.
Claims
What is claimed is:
1. A wireless telecommunication equipment having a receiver portion
and a transmitter portion, comprising:
an automatic gain control amplifier located in the receiver portion
of said equipment, said automatic gain control amplifier having a
first gain varied in accordance with an automatic gain control
signal input thereto; and
a transmission power control amplifier located in the transmitter
portion of said equipment, said transmission power control
amplifier having a second gain varied in accordance with an open
loop control signal input thereto,
wherein said automatic gain control amplifier and said transmission
power control amplifier have the same operating characteristic and
are comprised of amplifier devices, said amplifier devices having
the same characteristics and having the same bias voltage applied
thereto.
2. A wireless telecommunication equipment according to claim 1,
wherein said automatic gain control amplifier and said transmission
power control amplifier have the same gain characteristic in
accordance with a control signal input thereto when central gains
of their variable gain range are 0 dB.
3. A wireless telecommunication equipment according to claim 1,
wherein said automatic gain control amplifier and said transmission
power control amplifier have the same circuitry.
4. A wireless telecommunication equipment having a receiver portion
and a sender portion, comprising:
an automatic gain control amplifier located in the receiver portion
of said equipment, said automatic gain control amplifier having a
first central gain varied in accordance with an automatic gain
control signal input thereto;
a transmission power control amplifier located in the transmitter
portion of said equipment, said transmission power control
amplifier having a second central gain varied in accordance with an
open loop control signal input thereto; and
a plurality of fixed gain devices in said receiver and transmitter
portions of said equipment, said fixed gain devices have gains
allocated thereto which equalize said first central gain and said
second central gain.
5. A mobile station of a CDMA cellular phone system comprising:
a receiver portion, said receiver portion including an automatic
gain control amplifier having a first input for receiving an input
signal, a second input for receiving a gain control signal, and an
output;
a transmitter portion, said transmitter portion including a
transmission power control amplifier having a first input for
receiving a digital modulation signal, and a second input for
receiving an open loop control signal, said automatic gain control
amplifier and said transmission power control amplifier having
substantially the same circuit; and
a logic processing unit, said logic processing unit including
a receive signal strength detector for receiving the output of said
automatic gain control amplifier and having an output for
outputting the gain control signal to the second input of said
automatic gain control amplifier;
a closed loop power detector; and
an adder having a first input coupled to an output of said closed
loop power detector and a second input coupled to the output of
said receive signal strength detector, said adder outputting the
open loop control signal to the second input of said transmission
power control amplifier.
6. A mobile station of a CDMA cellular phone system according to
claim 5, wherein an orthogonal demodulator and an analog to digital
converter are interposed between the output of said automatic gain
control amplifier and an input of said receive signal strength
detector.
7. A mobile station of a CDMA cellular phone system according to
claim 5, wherein an integrator is interposed between the output of
said receive signal strength detector and the second input of said
adder.
8. A mobile station of a CDMA cellular phone system according to
claim 5 wherein a digital to analog converter is interposed between
said integrator and the second input of said automatic gain control
amplifier.
9. A mobile station of a CDMA cellular phone system according to
claim 7 wherein a digital to analog converter is interposed between
said integrator and the second input of said automatic gain control
amplifier.
Description
BACKGROUND OF THE INVENTION
This invention relates to wireless telecommunication equipment, and
in particular, to the mobile station of a code division multiple
access (CDMA) cellular phone system. The CDMA system, which employs
spread spectrum modulation, has a base station and a plurality of
mobile stations wherein each mobile station includes a receiver
portion and a transmitter portion, and is provided with a
transmission power controller.
In the CDMA system, each mobile station is provided with a spread
spectrum demodulator which despreads a received spread spectrum
signal in accordance with a distinctive spreading code assigned to
that mobile station. Each mobile station has a different spreading
code, and interference often occurs between the mobile stations.
The amount of interference depends on the correlation
characteristic of the spreading code of each mobile station.
As the interference occurring when a signal is sent from one mobile
station to another increases, the signal-to-noise ratio (S/N) of
the demodulated signal decreases. Consequently, the strength of the
radio wave transmitted by the mobile station must be constantly
changed as a function of the distance between the mobile station
and the base station, and to compensate for fading due to
variations in the transmission path. This means that to maximize
system capacity it is necessary to control transmission power so
that the radio signal transmitted from each mobile station to the
base station remains at the same level.
The transmission power of a conventional CDMA mobile station is
controlled by employing both open and closed loop control of the
power transmitted on a down channel from the base station to a
mobile station. In the open loop power control, the control
circuits of the mobile station initially assume that the radio
signal is attenuated in the same way in both the down channel and
in the up channel from the mobile station to the base station. An
estimate is made of the propagation loss in the down channel by
measuring the received power level at the mobile station,
predicting the power required for the up channel and using this
information to control the power transmitted by the mobile
station.
FIG. 2 is a graph showing the open loop power control
characteristic of a CDMA cellular portable telephone which complies
with the United States standard for CDMA telephones. In FIG. 2, the
transmission power of a mobile station is plotted against the
strength of the signal received at the mobile station and shows
that, using open loop power control, the dynamic range of the
transmission power must be at least 80 dBm. However, a closed loop
power control is also needed because the propagation losses of the
down and up channels are not the same since each channel uses a
different frequency band.
In the closed loop power control, the base station measures the
received signal strength, and sends a power control bit to a mobile
station along with normal information data at 1.25 ms intervals
using a down channel. The mobile station provides a fine control of
the transmitted power with a 1 dB pitch, which is in addition to
the transmitted power predicted by the open loop power control.
That is, the open loop power control provides an approximate or
rough control of the transmitted power, and the closed loop power
control performs a fine control of the transmitted power. However,
the characteristic of the conventional open loop power control is
such that the closed loop power control is nDt sufficiently
effective. Thus, there is a need for an improved open loop power
control.
The open loop power control characteristic of the conventional CDMA
cellular portable telephone standardized for use in the United
States has an allowable error in the transmitted power strength
which is within .+-.9.5 dBm despite variations in the environment
including changes in temperature. This is in comparison with the
received power (receive signal strength) vs. transmission power
(transmission signal strength) characteristic shown in FIG. 2.
However, the receiver and transmitter portions of conventional
mobile stations are comprised of power amplifiers and many other
functional components having individual gain variation
characteristics. These variations, added to variations in the
environmental temperature can result in the allowable error being
exceeded if the differences in gain variation between components of
the receiver and transmitter portions of the mobile station are
unduly large. In other words, using a conventional open loop power
control wherein the transmission signal strength in the transmitter
portion of the mobile station is controlled in accordance with the
strength of the received signal, the allowable error at a mobile
station could be exceeded if the difference in the gain variations
between the receiver and transmitter portions of the station is too
large. This problem occurs not only in mobile stations associated
with CDMA cellular portable telephone systems but also in other
wireless telecommunication equipment having open loop power
control.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a wireless
telecommunication equipment having a stable and desirable open loop
power control characteristic which compensates for variations in
the environment. It is another object of this invention to provide
a wireless telecommunication equipment having a receiver portion
including an automatic gain control amplifier and a transmitter
portion having a transmission power control amplifier which provide
a mobile station which is free from variations in gain despite
changes in the environment.
In accordance with the present invention, a wireless mobile
telecommunication equipment is provided having a receiver portion
and a transmitter portion, for example a CDMA cellular portable
telephone system which comprises an automatic gain control
amplifier located in the receiver portion and a transmission power
control amplifier located in the transmitter portion having first
and second gains respectively. The first gain is varied in
accordance with an automatic gain control signal input thereto, and
the second gain is varied in accordance with an open loop control
signal input thereto. Both the automatic gain control amplifier and
the transmission power control amplifier have the same operating
characteristic. Each of these amplifiers has the same bias applied
thereto, the same characteristics including the same central gain,
and the same circuitry. By central gain, is meant the midpoint of a
variable gain range of an amplifier.
In another aspect of the invention, a wireless telecommunication
equipment having a receiver portion and a transmitter portion
comprises an automatic gain control amplifier for changing a first
gain in accordance with an automatic gain control signal input to
the receiver portion, a transmission power control amplifier for
changing a second gain in accordance with an open loop control
signal input to the transmitter portion, and a plurality of fixed
gain devices. Each of the fixed gain devices has a gain allocated
thereto which equalizes the central gain of the automatic gain
control amplifier with the central gain of the transmission power
control amplifier.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and features of the invention may be understood with
reference to the following detailed description of an illustrative
embodiment of the invention, taken together with the accompanying
drawings in which:
FIG. 1 is a functional schematic block diagram showing a mobile
station according to an embodiment of the present invention;
FIG. 2 is a graph showing a standardized open loop power control
characteristic for a conventional CDMA cellular portable telephone
system;
FIG. 3 is a schematic block diagram showing a logic processing unit
according to the embodiment of the invention shown in FIG. 1;
and
FIG. 4 is a schematic diagram of a circuit which may be used as
both an automatic gain control amplifier and a transmission power
control amplifier for the embodiment of the invention shown in FIG.
1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The drawings illustrate a preferred embodiment of a mobile station
for a CDMA cellular telephone system used as a wireless
telecommunication equipment in accordance with the present
invention.
FIG. 1 is a functional schematic block diagram showing a mobile
station according to an embodiment of the present invention, and
FIG. 3 is a schematic block diagram showing a logic processing unit
8 comprising a part of the mobile station of FIG. 1.
Referring to FIGS. 1 and 3, an input signal received at a common
sending/receiving antenna 1 of a mobile station is input via a
duplexer 9 to a low noise amplifier (LNA) 2 comprising the first
stage of a receiver portion 16 of the mobile station. The LNA 2
amplifies the input signal with a fixed gain and inputs the
amplified signal to a band pass filter (BPF) 3 which removes
unnecessary signal components from the amplified input signal.
Then, a mixer 4 mixes the filtered signal with a local oscillation
signal obtained from a local oscillator (not shown), and the mixed
signal is down-converted to a digital modulation signal (IF signal)
in an intermediate frequency band, and output to an automatic gain
control amplifier (AGC) 5.
A gain control signal (RX AGC) is input to the AGC 5 from the logic
processing unit 8. The AGC 5 amplifies the IF signal with a gain
determined by the gain control signal RX AGC. A BPF 6 removes
unnecessary signal components from the amplified IF signal, and the
signal filtered by the BPF 6 is further amplified with a fixed gain
by a power amplifier (AMP) 7. The output of AMP 7 is output to the
logic processing unit 8 as an intermediate frequency band signal
(RX IF).
The logic processing unit 8, as shown in FIG. 3 comprises an analog
part 20 and a digital part 21. The analog part 20 includes an
orthogonal demodulator 22, an analog to digital (A/D) converter 23,
a digital to analog (D/A) converter 32 and an orthogonal modulator
33.
The RX IF signal output from AMP 7 is input to the orthogonal
demodulator 22. At the orthogonal demodulator 22, orthogonal
demodulation is performed on the digital modulator signal using a
local oscillation signal output from a local oscillator (not
shown). At the output of the demodulator 22, I phase (inphase) and
Q phase (quadrature phase) data signal components are output to the
A/D converter 23. These signal components are converted by the A/D
converter 23 to a digital base band signal RX I/Q, and output to a
conventional receive data processing circuit 34 where the digital
base band signal RX I/Q is de-spread using conventional spread
spectrum technology to provide a transmission symbol sequence. The
coventional receive data processing circuit 34 is for example
disclosed in OKI Technical review 156 Vol. 62, July 1996, p71-74
(esp., p72, left column, the fifth and sixth paragraphs) "CD3000B
Portable Telephone for CDMA Cellular Systems".
The base band signal RX I/Q is also input to a receive signal
strength detector 24 which generates receive electric field
strength data in accordance with the base band signal RX I/Q, and
outputs this data to an adder 25. The adder 25 outputs data
corresponding to the difference between the received electric field
strength data from the receive signal strength detector 24 and fine
adjustment power reference data (PREF) which is fixed and in
correspondence with desirable signal strength for the A/D converter
23 and the receive data processing circuit 34. The difference data
is integrated by an integrator 26, converted to an analog signal by
a D/A converter 27, and output to the AGC 5 as a gain control
signal RX AGC.
A base band signal TX I/Q is output from a conventional send data
processing circuit 35 using conventional spread spectrum
technology, as is for example disclosed in OKI Technical review 156
Vol.62, July 1996, p71-74 (esp., p72, left column, the forth
paragraph) "CD3000B Portable Telephone for CDMA Cellular Systems".
The signal TX I/Q includes an I phase data component and a Q phase
data component which are converted to an analog base band signal by
the D/A converter 32 and output to an orthogonal modulator 33. The
orthogonal modulator 33 orthogonally modulates the input base band
signal TX I/Q and generates a transmission signal (digital
modulation signal) in the intermediate frequency band (TX IF) by
using a local oscillation signal output from a local oscillator
(not shown).
The transmission signal TX IF is input to a transmitter portion 17
of the mobile station where it is amplified by a fixed gain
intermediate frequency amplifier AMP 15, unnecessary signal
components removed by a BPF 14, and the signal TX IF output to a
transmission power control amplifier AMP 13 for controlling the
transmission power. The TX AGC gain control signal from the logic
processing unit 8 is also input to AMP 13 which amplifies the
signal input from the BPF 14 by a gain determined by the gain
control signal TX AGC and outputs a transmnission signal to a
transmission mixer 12.
The gain control signal TX AGC is obtained as follows. As shown in
FIG. 3, the data corresponding to the receive power strength, which
is output from the integrator 26, is filtered by a Low Pass Filter
(LPF) 28 and output to an adder 29 as data for controlling the open
loop power. The adder 29 combines data output from a conventional
closed loop power controller 30, as is reqired in TIA/EIA/IS-95-A
page 6-6, section 6.1.2.3.2 "Closed Loop Output Power", for
controlling the closed loop power with the output of the -LPF 28,
and the sum of these data are output to a D/A converter 31. The D/A
converter 31 converts the input data to an analog signal and
outputs the analog signal to the AMP 13 as the gain control signal
TX AGC. When the receive power strength decreases, the gain control
signal TX AGC increases, and as a result the gain of the AMP 13 and
the transmission power is increased. When the receive power
increases, the transmission power is reduced.
As shown in FIG. 1, the transmission mixer 12 receives as an input
not only the transmission signal output from AMP 13 but also a
local oscillation signal of the transmission channel frequency band
which is output from a transmission channel frequency oscillator
(not shown). The mixer 12 up-converts the transmission signal from
the intermediate frequency band to the transmission channel band.
Unnecessary signal components of the transmission signal
up-converted to the transmission channel band are removed by a BPF
11, and output to power amplifier (PA) 10 which amplifies the
received signal by a fixed gain. The output signal of the PA 10 is
input to the common antenna 1 for broadcast via the duplexer 9.
In the mobile station, the gains of the fixed gain devices in the
receiver portion 16 of the mobile station, i.e., the LNA 2, BPF 3,
receiver mixer 4, BPF 6 and AMP 7, and the fixed gain devices in
the transmitter portion 17, i.e., the PA 10, BPF 11, transmission
mixer 12, BPF 14 and AMP 15 are allocated so as to equalize the
central gain of the AGC 5 with the central gain of the AMP 13.
Further, the AGC 5 in the receiver portion 16 and the AMP 13 in the
transmitter portion, which have the same central gain, also have
the same circuit which results in an open loop power control with a
better characteristic than that obtained with prior art CDMA
systems. More specifically, the AGC 5 and the AMP 13 are comprised
of amplifying devices having the same characteristic with respect
to variation in the environment such as temperature. In addition,
the same bias voltage is applied to the AGC 5 and AMP 13.
FIG. 4 is a schematic circuit diagram showing both the AGC 5 and
the AMP 13, these circuits being substantially identical. In the
following description, the AGC 5 will be described but it will be
understood that the description also applies to the AMP 13.
As shown in FIG. 4, the AGC 5 comprises three amplifying stages
consisting of field effect transistors Q1, Q2 and Q3, each having
an input gate terminal G1 and a control gate terminal G2. The gain
of the AGC 5 is variable and controlled by applying the gain
control signal RX AGC from the D/A converter 27 of the logic
processing unit 8 to the control gates G2 of transistors Q1, Q2 and
Q3 via gate resistances R1, R2 and R3. Similarly, the gain of the
AMP 13 is variable and controlled by applying the gain control
signal TX AGC from the D/A converter 31 of the logic processing
unit 8 to the control gates G2 of transistors Q1, Q2 and Q3 via
gale resistances R1, R2 and R3.
Since the AGC 5 in the receiver portion of the mobile station
affects the detected receive signal strength, and the AMP 13
affects the transmission power in the transmitter portion of the
mobile station, and since the AGC 5 and AMP 13 have the same
central gain and the same circuit, both the AGC 5 and the AMP 13
exhibit the same characteristic with respect to variations in the
environment including changes in temperature. Therefore, with
regard to the open loop power control, a lower error is achieved in
the open loop power control characteristics shown in FIG. 2 because
the gain variations of the AGC 5 and the AMP 13 caused by changes
in the environment are canceled by the interaction occurring at the
transmission power control amplifier stage 13. That is, a stable
and desirable open loop power control characteristic is
achieved.
In the mobile station, by allocating the gains of the fixed gain
devices in the receiver and transmitter portions, the AGC 5 which
affects detected data of a receive signal strength in the receiver
portion and the AMP 13 which affects transmission power in the
transmitter portion have the same central gain and the same circuit
so that stable and desired characteristics of the open loop power
control can be achieved in spite of variations in the environment
including temperature.
The positions of the automatic gain control amplifier in the
receiver portion and the transmission power control amplifier in
the transmitter system are not limited to that shown in the
described embodiment. For example, the AGC 5 can be placed at the
position of the AMP 7 shown in FIG. 1, and the AMP 13 can be placed
at the position of the AMP 15 in FIG. 1.
In general, the invention is applicable to wireless
telecommunication equipment of the type having a plurality of
automatic gain control and transmission power control amplifiers.
For example, in a wireless telecommunication equipment which
down-converts a received signal by means of a plurality of stages
and up-converts a transmission signal by means of a plurality of
stages, the wireless telecommunication equipment of the invention
may have a plurality of automatic gain control amplifiers and
transmission power control amplifiers.
The invention is applicable to wireless, telecommunication systems,
in general, and is not limited to the mobile station of a CDMA
cellular portable telephone system. Whether the wireless
telecommunication equipment has a closed loop power control or not
is not significant as long as it has an automatic gain control loop
in the receiver portion and an open loop power control.
As for the bias voltage described in the specific disclosed
embodiment, which is applied to and controls the operating voltage
of the automatic gain control amplifier and the transmission power
control amplifier, the bias voltage of the automatic gain control
amplifier is not necessarily the same as that of the transmission
power control amplifier if the characteristic of the other
components in the receiver and transmitter portions are suitably
adjusted.
While particular embodiments of the present invention have been
described and illustrated, it should be understood that the
invention is not limited thereto since modifications may be made by
persons skilled in the art. The present application contemplates
any and all modifications that fall within the spirit and scope of
the underlying invention described and claimed herein.
* * * * *